PubMed · 5929318
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S Afonso. 1966. A thermodilution flowmeter.. https://doi.org/10.1152/jappl.1966.21.6.1883
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We have investigated the effect of alpha(1)-adrenergic agonist phenylephrine (PE) on acetylcholine-activated K(+) currents (I(KACh)). I(KACh) was recorded in mouse atrial myocytes using the patch clamp technique. I(KACh) was activated by 10 microm ACh and the current decreased by 44.27 +/- 2.38% (n = 12) during 4 min due to ACh-induced desensitization. When PE was applied with ACh, the extent of desensitization was markedly increased to 69.34 +/- 2.22% (n = 9), indicating the presence of PE-induced desensitization. I(KACh) was fully recovered from desensitization after a 6-min washout. PE-induced desensitization of I(KACh) was not affected by protein kinase C inhibitor, calphostin C, but abolished by phospholipase C (PLC) inhibitor, neomycin. When phophatidylinositol 4,5-bisphosphate (PIP(2)) replenishment was blocked by wortmannin (an inhibitor of phophatidylinositol 3-kinase and phophatidylinositol 4-kinase), desensitization of I(KACh) in the presence of PE was further increased (97.25 +/- 7.63%, n = 6). Furthermore, the recovery from PE-induced desensitization was inhibited, and the amplitude of I(KACh) at the second exposure after washout was reduced to 19.65 +/- 2.61% (n = 6) of the preceding level. These data suggest that the K(ACh) channel is modulated by PE through PLC stimulation and depletion of PIP(2).
Neuronal loss within the basal ganglia has been hypothesized to play a role in movement disorders (e.g., tardive dyskinesia) that often occur following chronic neuroleptic treatment. Previous studies in animal models have provided some support to this possibility, but have not assessed regionally specific changes after chronic neuroleptic administration. The present study examined whether counts of neurons containing acetylcholine, described as large aspiny type II neurons, were altered in subregions of the corpus striatum and nucleus accumbens following chronic haloperidol administration in rats. Rats were administered haloperidol decanoate (21 mg/kg, i.m.) or vehicle every third week for 24 weeks. Following 4 weeks of withdrawal from the drug, predefined regions were examined for choline acetyltransferase (ChAT) immunoreactive (ir) cells. Compared to the vehicle group, the haloperidol group showed significant reductions in ChAT-ir cell counts in the ventrolateral striatum, nucleus accumbens core, and nucleus accumbens lateral shell. No significant differences were found in the other regions examined: dorsolateral striatum, dorsomedial striatum, ventromedial striatum, nucleus accumbens medial shell, and horizontal limb of the diagonal band. These findings indicate that there may be regionally specific alterations in ChAT-ir cells following chronic haloperidol treatment, supporting previous hypotheses of striatal cholinergic cell loss resulting from chronic neuroleptic treatment. More importantly, the regions affected (ventrolateral striatum and nucleus accumbens) are critical in the regulation of oral movements, thus suggesting that alterations in cholinergic cell activity, and perhaps actual loss of cholinergic cells in these regions, may be important in the manifestation of late-onset oral dyskinesia.
In the present study, the radiotracer [(18)F] (+)-4-fluorobenzyltrozamicol ((+)-[(18)F]FBT) and positron emission tomography (PET) were used to examine the vesicular acetylcholine transporter and determine if presynaptic cholinergic activity was altered with age in 23 rhesus monkeys that varied in age from 10 to 37 years. Binding of (+)-[(18)F]FBT in the basal ganglia was reduced significantly with increasing age of the monkeys. However, there were individual differences noted in that some middle-aged and aged monkeys demonstrated levels of (+)-[(18)F]FBT binding that were comparable to the binding measured in adult monkeys. These data indicate that presynaptic cholinergic function may decrease with age, but that there may be a differential susceptibility of the cholinergic system to the aging process in different individuals.